The Organic Light Emitting Display (OLED) device possesses many outstanding properties of self-illumination, low driving voltage, high luminescence efficiency, short response time, high clarity and contrast, near 180° view angle, wide range of working temperature, applicability of flexible display and large scale full color display. The OLED is considered as the most potential display device.
The OLED can be categorized into two major types according to the driving ways, which are the Passive Matrix OLED (PMOLED) and the Active Matrix OLED (AMOLED), i.e. two types of the direct addressing and the Thin Film Transistor matrix addressing. The AMOLED comprises pixels arranged in array and belongs to active display type, which has high lighting efficiency and is generally utilized for the large scale display devices of high resolution.
The OLED display element generally comprises a substrate, an anode located on the substrate, a Hole Injection Layer located on the anode, a Hole Transporting Layer located on the Hole Injection Layer, an emitting layer located on the Hole Transporting Layer, an Electron Transport Layer located on the emitting layer, an Electron Injection Layer located on the Electron Transport Layer and a Cathode located on the Electron Injection Layer. The principle of the OLED element is that the illumination generates due to the carrier injection and recombination under the electric field driving of the semiconductor material and the organic semiconductor illuminating material. Specifically, the Indium Tin Oxide (ITO) electrode and the metal electrode are respectively employed as the anode and the cathode of the Display. Under certain voltage driving, the Electron and the Hole are respectively injected into the Electron and Hole Transporting Layers from the cathode and the anode. The Electron and the Hole respectively migrate from the Electron and Hole Transporting Layers to the Emitting layer and bump into each other in the Emitting layer to form an exciton to excite the emitting molecule. The latter can illuminate after the radiative relaxation.
The OLED panel technology based on the printing skill becomes the advanced and new technology at present. The technology uses ink jet printing process to manufacture the organic functioning layers (including the hole injection layer, the hole transporting layer, the light emitting layer, the electron transporting layer and the electron injection layer) of the OLED element and can tremendously promote the usage efficiency of the OLED material to reduce the production cost of the OLED panel, and meanwhile, possesses the technical potential of manufacturing the flexible OLED panel, and the large-scale research on this technology has become the development direction of OLED display.
In the process of printing the OLED material, one manufacture process of the hydrophobic pixel definition layer (bank) play a decisive role of the following success printing of the OLED material. The function of the hydrophobic pixel definition layer is to implement the pixel definition to form the red (R) pixel regions, the green (G) pixel regions and the blue (B) pixel regions. Then, the OLED material will be printed in these pixel regions. In order to enable the OLED material to 100% enter into the pixel regions, the pixel definition layer requires absolute surface hydrophobicity so that as printing, the OLED material will not stay on the top of the pixel definition layer and even flows into the adjacent pixel region to result in color mixing. In order to realize the absolute surface hydrophobicity of the pixel definition layer, the common means for now is to add hydrophobic substances in the ordinary organic photoresist material to obtain the hydrophobic organic photoresist material. Then, the hydrophobic organic photoresist material is used to manufacture the pixel definition layer. The surface of the ultimately resulting pixel definition layer possesses the hydrophobic characteristic. However, the process of the method is complicated and the surface hydrophobicity of the resulting pixel definition layer is often not ideal, the issue that the OLED material stays on the top of the pixel definition layer as printing or the caused color mixing cannot be effectively solved.